PPG sensor having light arrival angle control at detector

Abstract

The present disclosure generally relates to wearable devices and methods for measuring a photoplethysmographic (PPG) signal. The wearable devices and methods described herein are capable of obtaining PPG signals by employing a PPG sensor array configured to receive light at angles associated with a high perfusion index. Viewing components may be coupled to the PPG sensor array to effect transmission of light at these preferential angles.

The invention claimed is: 
     
       1. A wearable device for monitoring a physiological parameter of an individual, comprising:
 a housing having a skin-contacting surface; 
 a light emitter positioned within the housing and configured to emit light towards a skin of the individual when the skin-contacting surface is positioned at the skin of the individual; 
 a plurality of light sensors, wherein each of the plurality of light sensors is configured to detect light output from the light emitter that has interacted with a tissue region associated with the skin of the individual; 
 a first viewing component that coupled with a first light sensor of the plurality of light sensors, and positioned at a first separation distance from the light emitter, the first viewing component configured to:
 allow light transmitted from the light emitter and received from the tissue region of the individual at a first preselected angle of incidence to pass through to the first light sensor, and 
 block light at angles other than the first preselected angle of incidence, wherein the first preselected angle of incidence is based at least in part on the first separation distance; 
 
 a second viewing component coupled with a second light sensor of the plurality of light sensors, and positioned at a second separation distance from the light emitter, the second viewing component configured to:
 allow light transmitted from the light emitter and received from the tissue region of the individual at a second preselected angle of incidence, different from the first preselected angle of incidence, to pass through to the second light sensor; and 
 block light at angles other than the second preselected angle of incidence, wherein the second preselected angle of incidence is based at least in part on the second separation distance; 
 wherein the first separation distance is less than the second separation distance and the first preselected angle of incidence is less than the second preselected angle of incidence; and 
 
 a processor within the housing and in communication with the plurality of light sensors, wherein the processor is configured to compute the physiological parameter based on the light detected by the plurality of light sensors. 
 
     
     
       2. The wearable device of  claim 1 , wherein the first viewing component is disposed over the first light sensor, and
 the second viewing component is disposed over the second light sensor. 
 
     
     
       3. The wearable device of  claim 1 , wherein the first light sensor is configured to detect light of a first wavelength. 
     
     
       4. The wearable device of  claim 3 , wherein the second light sensor is configured to detect light of a second wavelength. 
     
     
       5. The wearable device of  claim 4 , wherein the first wavelength is the same as the second wavelength. 
     
     
       6. The wearable device of  claim 4 , wherein the processor receives first data from the first light sensor and second data from the second light sensor,
 wherein the first data and the second data each comprise physiological data pertaining to the same tissue region, and 
 wherein the processor is configured to compute the physiological parameter based on the physiological data. 
 
     
     
       7. The wearable device of  claim 1 , wherein:
 the plurality of light sensors includes a first set of light sensors comprising the first and second light sensors configured to measure a first wavelength and a second set of light sensors configured to measure a second wavelength; 
 the first set of light sensors are optically coupled to a first set of viewing components comprising the first and second viewing components; 
 the second set of light sensors are optically coupled to a second set of viewing components; and 
 at least one of the second set of viewing components is configured to block light at angles other than the first preselected angle of incidence. 
 
     
     
       8. The wearable device of  claim 7 , wherein the first set of light sensors is interleaved with the second set of light sensors. 
     
     
       9. The wearable device of  claim 1 , wherein:
 the plurality of light sensors includes:
 a first set of light sensors comprising the first and second light sensors configured to measure a first tissue region; 
 
 a first set of view components comprising the first and second viewing components; and
 a second set of light sensors configured to measure a second tissue region; 
 
 at least one of the second set of light sensors is coupled to at least one viewing component of a second set of viewing components; and 
 the at least one viewing component of the second set of viewing components is configured to block light at angles other than the first preselected angle of incidence. 
 
     
     
       10. The wearable device of  claim 9 , wherein:
 the light emitter is a first light emitter; 
 the first set of viewing components is optically coupled to the first light emitter; 
 the second set of viewing components is optically coupled to a second light emitter; and 
 a separation distance between the first set of viewing components and the first light emitter is the same as a separation distance between the second set of viewing components and the second light emitter. 
 
     
     
       11. The wearable device of  claim 1 , wherein the plurality of light sensors are configured as an array of light sensors, each light sensor optically coupled to a different viewing component, each viewing component having a different preselected angle of incidence.